Fix HTML (fixes #1707)

gui/index.html

@@ -1007,7 +1007,7 @@
         <a href="#" ng-click="neededChangePageSize(option)">{{option}}</a>
       <li>
     </ul>
-    <div class="clearfix">
+    <div class="clearfix"></div>
   </modal>
 
   <!-- About modal -->